increasing attention because the electrochemical behaviour of UMEs was found to be
uniquely different from that of conventional electrodes. One of the most attractive aspects of
UMEs is their capability of monitoring reactions occurring an ultrasmall regions such as
intracellular environments [l-3]. The UMEs also work as probes to obtain local information on
solid surfaces [4]. The redox current observed at the UME placed close to the surface is …